Absolute Flux Calibrations for the Nancy Grace Roman Space Telescope Coronagraph Instrument

TL;DR

This paper presents an absolute flux calibration method for the Roman Space Telescope's Coronagraph Instrument, achieving a 1.94% error using standard stars and a 22-minute observation plan to ensure high-precision flux measurements.

Contribution

It introduces a flux calibration approach utilizing HST CALSPEC stars to attain high accuracy for Roman's coronagraph observations.

Findings

Achieved 1.94% AFC error with 22-minute observations.

Utilized 14 standard stars from HST CALSPEC catalog.

Accounted for systematic uncertainties and shot noise.

Abstract

The Nancy Grace Roman Space Telescope's (Roman) Coronagraph Instrument is a technology demonstration equipped to achieve flux contrast levels of up to 10$^{-9}$. This precision depends upon the quality of observations and their resultant on-sky corrections via an absolute flux calibration (AFC). Our plan utilizes 10 dim and 4 bright standard photometric calibrator stars from Hubble Space Telescope's (HST) CALSPEC catalog to yield a final AFC error of 1.94\% and total observation time of $\sim$22 minutes. Percent error accounts for systematic uncertainties (filters, upstream optics, quantum efficiency) in Roman component instrumentation along with shot noise for a signal to noise ratio (SNR) of 500.